THE BA C TERIOLOGICA L LA BORA TOR Y 15 



high-power objectives is impaired when this instru- 

 ment is used. It is believed by some that when 

 the monocular microscope is used continuously the 

 eyes are apt to become fatigued. The student 

 should learn to 

 keep both eyes 

 open when work- 

 ing with the 

 monocular micro- 

 scope. There are 

 several ways by 

 which this may 

 be effected. One 

 is by having a 

 black sheet of 

 paper near to the 

 second eye; an- 

 other plan is to 

 put the hand be- 

 fore the eye. 

 Perseverance is 

 all that is needed. 

 One evening is 

 quite enough to 

 make any one 

 skilful, if he is 

 determined to ' 

 succeed. The 

 student need no 

 more fear seeing things on the table with the 

 second eye than seeing the crown of his head, unless 

 he is^training for drawing objects -on the table by 



FIG. 3. ZEISS' MICROSCOPE. 



